Disconnected movement is easy to spot. Endo, Sensei certainly is not disconnected.
I am not going to comment on Endo Sensei's movement, not my place without feeling his movement. I agree with Dan that you can get a feel for what is happening by watching...some are good at this and some (many) are "less good" at it.. My comments from watching the video would be more about the uke 'disconnecting' from the attack running before the response. No problem with that though in the process you need to keep enough connection back though the response to help you understand where it is going. Things can change in the movement and you want to know what the changes are so you can protect yourself and be able to put yourself in the position to counter/respond/whatever.
The ability to move the shoulders as a independent joint intrigues me. Uriah Faber uses his shoulders to strike when he has his opponent up against the cage. That made me think.
To me care needs to be taken that one just removes substance from the shoulder and does not disconnect. The shoulder, to me, is not independent rather still just part of the whole as you move to secondary pressure and maybe even further back than that. I can stand still and roll my shoulders independent of the rest of my body.....it is disconnected and on its own. I don't think you are talking about that.